Despite having span a full season with 25 episodes, it's still short compared to something like Detective Conan, and it also doesn't have as many puzzles. The few puzzles are interesting and challenging, and always ends in most unexpected ways. This punchline-like attribute makes Spiral a very exciting series that's worth watching ^_^

The puzzles, the music, and Hiyono ;) Hiyono is the best! She is not just a sub character, she is the highlight of the whole series... her song and especially her previews are just priceless ^_^

Although the series may seem incomplete near the end, it's still a very cool series. Even more so with Hiyono in it ;)